Will Sickle Cell Be the Next Disease Genetic Engineering Cures?

Sickle cell disease is a slow, vicious killer. Most people diagnosed with the red blood cell disorder in the US live to be between 40 and 60. But those years are a lifetime of pain, as abnormal, crescent-shaped haemoglobin stops up blood flow and deprives tissues of oxygen, causing frequent bouts of agony, along with more severe consequences like organ damage. Now, after decades of searching for a cure, researchers are announcing that, in at least one patient, they seem to have found a very promising treatment.

Two years ago, a French teen with sickle cell disease underwent a gene therapy treatment intended to help his red blood cells from “sickling.” In a paper published Thursday in the New England Journal of Medicine, the researchers revealed that today, half of his red blood cells have normal-shaped haemoglobin. He has not needed a blood transfusion, which many sickle cell patients receive to reduce complications from the disease, since three months after his treatment. He is also off all medicines.

To reiterate, the paper is a case study of just one patient. Bluebird Bio, the Massachusetts biotech company that sponsored the clinical trial, has treated at least six other trials underway in the US and France, but those results have not yet been fully reported. The gene therapy has not worked quite as well in some of those other patients; researchers say they are adjusting the therapy accordingly. It is also possible that the boy may eventually experience some blood flow blockages again in the future.

The results, though early, are encouraging. They represent the promise of new genetics technologies to address a disease that has long been neglected and tinged with racism. Sickle cell disease affects about 100,000 people in the US, most of whom are black. It is an inherited genetic disease caused by a mutation of a single letter in a person’s genetic code.

This single-letter mutation makes it a promising candidate for cutting edge technologies, like the gene-editing technique CRISPR-Cas9, and other gene therapies. Recently, a rush of new research has sought to address it. Two other gene therapy studies for sickle cell are underway in the US —one at UCLA and another at Cincinnati Children’s Hospital. Yet another is about to start in a collaboration between Harvard and Boston Children’s Hospital. Last fall, researchers all demonstrated the ability to correct the mutation in human cells using CRISPR, though that strategy will yet have to surpass significant scientific and political hurdles before reaching clinical trials.

In the new study, researchers took bone marrow stem cells from the boy and fed them corrected versions of a gene that codes for beta-globin, a protein that helps produce normal haemoglobin. The hope was that those altered stem cells would interfere with the boy’s faulty proteins and allow his red blood cells to function normally. They continued the transfusions until the transplanted cells began to produce normal-shaped haemoglobin. In the following months, the numbers of those cells continued to increase until in December 2016, they accounted for more than half the red blood cells in his body. In other words, so far so good.

Currently, the only long-term treatment for sickle cell disease is a bone marrow transplant, a high-risk, difficult procedure which many patients are not even eligible for. Pain and other side-effects are treated with blood transfusions for temporary relief. New technologies offer the hope of a solution that could provide long-term relief and allow patients to live some semblance of a normal life.

For decades, gene therapies have been touted as a cure for everything. But so far, successes have been infrequent, and often for very rare diseases. But early success in treating sickle cell disease means that soon, if we’re lucky, the benefits of this technology may reach hundreds of thousands of people. [New England Journal of Medicine]